CH690908A5 - Hydraulic press has T-shaped body with sections containing pressure, control and support pistons - Google Patents

Abstract

The press, e.g. for opening and closing the jaws of a drawing-blowing mould, consists of a T-shaped body (9) with three branches, a first branch (10) containing a pressure piston (17), a second (11) with the control piston (40) actuating the pressure piston by a fluid contained in a chamber (26), and a third branch (12) containing a piston (70) actuated by pressure fluid. The chamber (26) is located between the three pistons and can be divided by a valve (44) into two partial chambers (21, 42) so that the control piston moves the pressure piston when the valve is open and the third piston acts on the pressure piston when the valve is closed.

Description

The present invention relates to a hydraulic press comprising at least one frame and, arranged in this frame, a press piston and a control piston intended to move the press piston by means of a liquid contained in a chamber.

Presses of this kind are known and used in different applications and in particular for controlling the closing and opening of the mold jaws in stretch-blow molding devices. The known presses, however, are of considerable size and slow and unsuitable operation.

The object of the present invention is to remedy these drawbacks and it is characterized for this purpose by the fact that the frame comprises three branches, a first branch containing the press piston, a second branch containing the control piston subjected to the action of a source of pressurized fluid, and a third branch containing at least a third piston subjected to the action of at least one source of pressurized fluid, said chamber being arranged between the three pistons and capable of being divided at by means of at least one valve in two partial chambers, so that the control piston moves the press piston when the valve is open, and so that the third piston acts on the press piston when the valve is closed to form a partial chamber between the third piston and the press udder.

By these characteristics, an excellent closure of the molding members is obtained, rapid operation and a reduced size of the press.

Favorably, the press piston is subjected to the action of a source of pressurized fluid in a direction opposite to the action exerted on the control piston so that the liquid contained in said chamber is subjected at all times to a pressure higher than atmospheric pressure.

By these measures, the hydraulic fluid, generally oil, can be preserved without degradation over a long period and the application of the high closing pressure is ensured reliably so that no air intake can accidentally get occur in the oil chamber.

According to an advantageous embodiment, the pistons and the valve each comprise at least one part visible from the outside of the frame.

All the functions of the moving parts can thus be checked by simple visual inspection, and possible failures can be detected immediately, which allows great press security.

Preferably, the three branches form a general T-shaped arrangement, the control piston and the third piston having substantially parallel axes.

These features allow easy access to each component of the press and a particularly small footprint.

Favorably, the third piston is constituted by at least two superimposed partial pistons arranged one after the other, each partial piston being subjected to the action of a source of pressurized fluid.

The adjustment of the high closing pressure can thus be carried out in a precise manner, which allows a particularly advantageous use of the press in a blow molding or stretch-blow molding device.

According to an advantageous embodiment, the control piston and the press piston are subjected to the action of a first source of fluid having a first range of pressures, the third piston or each of the partial pistons of the third piston being subjected to at least a second fluid source having a second pressure range higher than the first range.

These characteristics ensure particularly reliable and rapid operation.

The invention also relates to a use of the hydraulic press in a blow molding device having n molding cavities each subjected to the action of a source of fluid having said second range of pressures, and is characterized in that the third piston comprises n superimposed partial pistons, each of the partial pistons being subjected to the action of one of the sources of fluid having a pressure corresponding to one of the sources of fluid having said second range of pressures associated with the mold cavities.

An excellent self-balancing of the closing pressure of the molding members is thus obtained, allowing great manufacturing reliability, while avoiding any deterioration of the molding members by too great closing pressure.

According to a preferred embodiment, the molding device comprises at least one movable jaw arranged so that its movements in the open and closed position are effected under the effect of the movements of the control piston and of the press piston subjected to the action of the first source of fluid having said first range of pressures when the valve is in the open position, and so that its maintenance in the closed position is obtained by the action of the third piston whose partial pistons are subjected to the action of said sources of fluid having said second range of pressures, when the valve is in the closed position.

By separating the functions relating to the movement and the maintenance in the closed position of the movable jaw, a particularly reliable operation is obtained, allowing rapid closure and opening, while ensuring that the closed position is secure and of adequate strength.

Other advantages appear from the characteristics expressed in the dependent claims and in the description setting out the invention below in more detail with the aid of drawings which schematically and by way of example show an embodiment.

 Fig. 1 is a sectional view of the press.  Figs. 2A to 2D are sectional views of the press in different operating positions.  Fig. 3 illustrates the press connected to a molding device of a stretch-blow molding machine.

The press 1 illustrated in FIG. 1 comprises a frame 9 having three branches 10, 11, 12. These three branches form a general T-shaped arrangement. The branch 10 comprises a press cylinder 15 fixed at one of its ends to the other two branches 11 and 12 and closed at its other end by a cover 16. A press piston 17 is slidably mounted in the cylinder 15 and comprises a free end 18 passing through the cover 16 and intended to cooperate with a jaw of a stretch-blow molding device. The front surface 20 of this piston faces a central chamber 21. An annular chamber 22 is delimited by the press piston 17 and the internal wall of the cylinder 15 and of the cover 16 and comprises an active surface 23. This annular chamber 22 is connected by a conduit 25 to a low pressure circuit 24 comprising a source of low pressure fluid, such as compressed air, having a pressure range between 1 and 10 bars, preferably 6 to 8 bars. Two seals 27, 28 are arranged between the press piston 17 and its cylinder 15 and a seal 29 is interposed between the cover 16 and the press piston 17. A hole 30 connects the contact surface between the front part 31 of the piston 17 and the cylinder 15 with the outside of the free end 18 of the press piston 17, and serves as a purge.

The branch 11 comprises a low pressure control cylinder 35 fixed to an intermediate sleeve 36 and closed at its free end by a cover 37. A low pressure control piston 40 is slidably mounted in the cylinder 35 and comprises a directed surface 41 towards a lateral chamber 42 which is connected with the central chamber 21 by a passage 43 provided in the sleeve 36. A valve 44 is arranged in the passage 43 and cooperates with a seat 45 to open or close the passage between the lateral and central chambers . An annular chamber 50 is delimited by the control piston 40 and the internal wall of the cylinder 35 and of the cover 37. It has an active surface 51 and is connected by a conduit 52 to said low pressure circuit 24. Two seals 54, 55 are arranged between the control piston 40 and its cylinder 35 and a seal 56 is interposed between the cover 37 and the press piston 40. A hole 58 connects the contact surface between the front part 59 of the piston 40 and the cylinder 35 with the outside of the free end 60 of the piston 40, and serves as a purge. This free end also comprises a filling orifice for the hydraulic fluid closed by a plug 62.

The passage 43 has a funnel shape flaring towards the lateral chamber 43, so as to facilitate the flow of the hydraulic liquid, preferably an oil, from the lateral chamber 42 towards the central chamber 21. The valve 44 which is arranged in the intermediate sleeve 36 has a large section with a diameter of 40 mm ensuring a high oil flow and a short stroke allowing rapid closing and opening. It is preferably pneumatically operated.

The third branch 12 comprises a high pressure device 64 having a three-stage cylinder 65, 66, 67, 68, in which is slidably mounted a high pressure piston 70 comprising three partial pistons 71, 72, 73 superimposed, housed in the three floors. Each stage is connected by a conduit 75, 76, 77 to a source of fluid under high pressure, which corresponds to the source of fluid used for blowing for each of three molding chambers of the stretch-blow molding device. The range of pressures used is generally between 11 and 50 bars, preferably 40 bars. Each partial piston 71 to 73 forms with the wall of the corresponding stage 66 to 68 an annular chamber 80, 81, 82 in which the associated conduit 75 to 77 terminates.

The piston 70 comprises a piston head 74 housed in a cylinder head 69 and forms with the latter an annular recoil chamber 83 connected by a conduit 78 to the exhaust and to the source of low pressure fluid, which allows assist the recoil movement of the piston 70.

Seals 85 are arranged between each partial piston 71 to 73 and each stage 66 to 68, and between the head of the piston 74 and the cylinder head 69. A hole 87 connects the contact surface between the cylinder head 69 and the piston head 74 with the outside of the branch 12, and serves as a purge. This branch 12 further comprises a milling 88 made between the cylinder head 69 and the first stage 65. This milling which connects the inside of the cylinder 65 to the outside serves as a separating element between the front part with low pressure supply via the conduit 78 and the rear part with high pressure supply via the conduit 75. This milling 88 allows the evacuation of air from accidental leaks, which risk damaging the fluid or low pressure air supply circuit. The cylinder 65 also comprises millings 89, 90 between stages 66 and 67 and stages 67 and 68 intended to connect the front part of the partial pistons 72 and 73 to atmospheric pressure. By the superposition of these three partial pistons, the third piston 70 acts in a way as a pressure multiplier.

The two central and lateral chambers 21 and 42 form a single oil chamber 26 of which only one part 21 can be put under high pressure by the action of the piston 70 after closing the valve 44, but the two parts of which can be put under low pressure by the action of pistons 17 and 40 after opening of valve 44.

Since the second branch 11 is preferably mounted vertically upwards, as illustrated in FIG. 1, any air bubbles present in the hydraulic fluid during filling tend to rise inside the chambers 21 and 42, as well as in the control piston 40. They can be evacuated by a purge valve provided in the plug 62. The chambers 21 and 42 are for this purpose advantageously shaped so as to have no part which could hinder the flow of the air bubbles towards the plug 62.

The conduits 25 and 52 are both connected to the same low pressure circuit 24 via a control valve 92. The latter is advantageously of the proportional type, and adjusted so as to put the oil chamber 26 at all times under positive pressure compared to atmospheric pressure. This prevents air from entering the oil chamber 26 which could compromise the subsequent application of high pressure and cause rapid degradation of the oil.

The press 1 operates as follows with reference to FIGS. 2A to 2D. In a first phase (fig. 2A and 2B), the valve 44 is open. The control piston 40 of branch 11 pushes, via the engine liquid, with rapid movement, the press piston 17 of branch 10. This movement is controlled by valve 92 which sends pressurized air in the annular chamber 50 of the branch 11 and gradually lets out the air contained in the annular chamber 22 of the branch 10, the oil chamber 26 between the pistons 17 and 40 is however always subjected to a positive pressure with respect to atmospheric pressure.

The valve 92 is arranged so as to precisely control the acceleration and deceleration of the movement of the pistons 17 and 40 at the end of the stroke. According to a favorable variant, the cross sections of the pistons 17 and 40 are identical.

When the press piston 17 has moved a predetermined distance and / or the pressure in the chamber 50 of the branch 11 has reached a predetermined value, the valve 44 is closed, for example by means of a pneumatic control ( fig. 2C). The high pressure is then applied to the conduits 75 to 77 of the branch 12, each conduit being subjected to a pressure corresponding to the pressure prevailing in one of the molding chambers of the stretch-blow molding device (FIG. 2D). This balances the pressures prevailing in the molding chambers and those acting on the pistons 17 and 70, which makes it possible to prevent the molding device from being damaged by too high a press pressure.

The reverse movement of the press piston 17 is obtained by exhausting the conduits 75 to 77, by opening the valve 44 and by applying the low pressure in the annular chamber 22.

All the movements and the functioning of all the mobile elements of the press, and in particular of the pistons 17, 40, 70 and of the valve 44 are visible from the outside of the press. Any failures can be noticed immediately by simple visual inspection.

The separation into two high and low pressure circuits ensures a very rapid and controlled movement of the press piston 17 and the subsequent application of a high closing pressure of the mold, which is balanced in force with respect to the pressure prevailing in the mold .

The T-shaped arrangement of the three branches allows easy access to each component of the actuator and a reduced bulk. It allows an adequate integration in the interior space of stretch blow molding machines.

Fig. 3 illustrates the use of the hydraulic press 1 in relation to a molding device 100 of a machine for manufacturing a container by stretch-blowing. In the latter, preforms 102 are arranged neck down in tubular supports 103 mounted on carriers 104 moved along a guide path.

The molding device 100 comprises a fixed jaw 107 and a movable jaw 108, in which two halves of three molding cavities 110 are aligned. Only the first molding cavity 110 is visible in FIG. 3. Three mobile blowing nozzles 111, only one of which is visible in FIG. 3, are intended to be applied against the lower opening of the tubular supports 103. Each endpiece 111 is connected, via a conduit 112 and a valve 113, to the source of fluid 114 under high pressure, generally air at a pressure range between 11 to 50 bars, preferably 40 bars. Each of the supply conduits 75 to 77 of the stages 66 to 68 of the cylinder 65 is also connected to one of the conduits 112, so that the pressure prevailing in one of the molding cavities 110 is identical to the pressure prevailing in one of the stages 75 to 77 of the third cylinder 65. The active surfaces of the annular chambers 80 to 82 (fig. 1) acting on the partial pistons 71 to 72 relative to the surface of each of the molding cavities 110 are calculated so that the movable jaw 108 is applied against the fixed jaw 107 with sufficient force preventing the opening of the molding device 100.

After introduction of three preforms 102 into the molding device 100, the valve 92 is actuated so that the low pressure circuit 24 advances the pistons 40 and 17 to apply the movable jaw 108 against the fixed jaw 107. The valve 103 is then closed and the stretch-blow molding operation can be carried out by connecting each end piece 111 and each stage 66 to 68 corresponding to the high pressure source 114.

After the containers have been formed, the conduits 112 are exhausted, the valve 44 is opened and the valve 92 is actuated so that the pistons 17 and 40 move back to move the movable jaw 108 away from the fixed jaw.

It is understood that the embodiment described above has no limiting character and that it can receive any desirable modifications within the framework as defined by claim 1. In particular, the three branches 10, 11 , 12 could be arranged in a different geometry, for example in the form of a Y. The press could comprise more than one valve 44 making it possible to adjust the flow rate of the liquid in the passage 45. The active surfaces, the purges and the linings of the pistons could be arranged differently. The central and lateral rooms could have a completely different shape and layout. The press could be designed for any other use in which rapid movement followed by a controlled application force is desirable. The number of stages of the cylinder 65 could be different from three and chosen between 2 and 6 for example. This number of stages and partial pistons will however be coordinated with the number of tools that the press is intended to actuate.

Instead of having at least two sources of fluid with a higher and lower pressure range, it may alternatively have only one source of fluid applied on the one hand to the control and press pistons to effect rapid displacements. and, on the other hand, on each of the partial pistons of the third piston acting as a pressure multiplier to maintain the position.

Claims (10)

1. Hydraulic press comprising at least one frame (9) and, arranged in this frame, a press piston (17) and a control piston (40) intended to move the press piston by means of a contained liquid in a chamber (26), characterized in that the frame (9) comprises three branches (10, 11, 12), a first branch (10) containing the press piston (17), a second branch (11) containing the control piston (40) subjected to the action of a source of pressurized fluid, and a third branch (12) containing at least a third piston (70) subjected to the action of at least one source of fluid under pressure, said chamber (26) being arranged between the three pistons (17, 40, 70) and capable of being divided by means of at least one valve (44) into two partial chambers (21, 42), so that the control piston (40) moves the press piston (17) when the valve (44) is open, and so that the third piston (70) acts on the pi press ston (17) when the valve (44) is closed to form a partial chamber (21) between the third piston (70) and the press piston (17). 2. Hydraulic press according to claim 1, characterized in that the press piston (17) is subjected to the action of a source of pressurized fluid in a direction opposite to the action exerted on the control piston ( 40), so that the liquid contained in said chamber (26) is subjected at all times to a pressure greater than atmospheric pressure. 3. Hydraulic press according to claim 1 or 2, characterized in that the valve (44) has a section large enough to ensure rapid flow of the fluid. 4. Hydraulic press according to one of claims 1 to 3, characterized in that the pistons (17, 40, 70) and the valve (44) each comprise at least one part (18, 60, 73) visible from the exterior of the frame (9). 5. Hydraulic press according to one of claims 1 to 4, characterized in that the three branches (10, 11, 12) form a general T-shaped arrangement, the control piston (40) and the third piston (70) having substantially parallel axes. 6. Hydraulic press according to one of claims 1 to 5, characterized in that the third piston (70) consists of at least two superimposed partial pistons (71, 72, 73) arranged one after the other, each partial piston being subjected to the action of a source of pressurized fluid. 7. Hydraulic press according to one of claims 1 to 6, characterized in that the control piston (40) and the press piston (17) are subjected to the action of a first source of fluid having a first pressure range, the third piston (70) or each of the partial pistons (71, 72, 73) of the third piston being subjected to at least one second source of fluid having a second pressure range higher than the first range. 8. Use of the hydraulic press according to claim 7, in a blow molding device (100) having n molding cavities (110) each subjected to the action of a source of fluid (114) having said second range of pressures, characterized in that the third piston (70) comprises n superimposed partial pistons (71, 72, 73), each of the partial pistons being subjected to the action of one of the sources of fluid having a pressure corresponding to the one of the fluid sources (114) having said second range of pressures associated with the mold cavities (110). 9. Use according to claim 8, characterized in that n is between 2 and 6, preferably 3. 10. Use according to claim 8, characterized in that the molding device (100) comprises at least one movable jaw (108) arranged so that its movements in the open and closed position are effected under the effect of displacements of the control piston (40) and of the press piston (17) subjected to the action of the first source of fluid having said first range of pressures when the valve (44) is in the open position, and so that its maintenance in the closed position is obtained by the action of the third piston (70) whose partial pistons (71, 72, 73) are subjected to the action of said sources of fluid (114) having said second range of pressures, when the valve (44) is in the closed position.